Insulating glass units

ABSTRACT

Insulating glass units sealed with a gradient cure hot-melt butyl rubber sealant composition are disclosed.

This is a divisional, of application Ser. No. 626,230 filed Oct. 28,1975, now U.S. Pat. No. 3,998,680.

BACKGROUND OF THE INVENTION

Insulating glass units are well-known. They generally comprise at leasttwo sheets of glass spaced from one another by a spacer element therebyproviding a dead or insulating air space between the panes of glass.Many attempts have been made to hermetically seal insulating glass unitsso as to provide a barrier against air, dust, and water vapor. Typicalmethods used to seal insulating glass units are described in U.S.Letters Pat. Nos. 3,759,771 and 3,852,149.

The types of sealants previously used in preparing insulating glassunits include sealants made from polysulfide materials which cure orcrosslink at room temperature after application to the insulating glassunit. Such sealants provide adhesion of a chemical nature involving achemical bond between glass, the metal spacing member and the sealant,generally brought about through a chemical intermediate.

Another type of sealant consists of uncrosslinked polymers such as butyland polyisobutylene applied by hot-melt application. Hot-melt sealants,particularly those made from butyl rubber, plasticizers and fillers areuseful insulating glass sealants since they possess inherently low watervapor transmission rates. Since hot-melt butyl sealants usually containno solvents, shrinkage is minimal after these materials have beenapplied to an insulating glass unit and completely crosslinked or cured.Adhesion in such systems is usually of a physical nature employing thetacky properties of the butyl base polymers and any additives whichcontribute to tack. It is necessary, however, to apply mechanicalbanding about the periphery of insulating glass units sealed with thistype of hot-melt sealant to prevent movement of the sealant due tocreep, cold flow, stress or excessive temperature changes.

Another type of sealant comprises the application of uncrosslinkedpolymers in tape form or hot-melt form followed by the application of asecond crosslinking sealant about the perimeter of the insulating glassunit to add structural strength. This type of sealant is particularlydesirable since it provides both chemical and physical adhesion of theglass and spacer element making up the insulating glass unit. Further,in the event either of the sealants shall fail, the remaining sealantmay be sufficient to maintain the integrity of the unit.

Regardless of the type of sealant used in forming the insulating glassunit, the function of the sealant is two-fold. First, the sealant is toprovide and maintain the insulating glass unit in a hermetically sealedstate and, second, the sealant should have adhesive properties whichfunction to hold the glass panes and spacer element in a predeterminedconfiguration.

An object of this invention is to provide an insulating glass unit and amethod of fabricating insulating glass units with a single applicationsealant which will serve to hermetically seal the insulating glass unitand provide adhesive properties serving to maintain the insulating glassunit in a desired assembled configuration.

A further object is to provide a method for fabricating insulating glassunits with a single application sealant having the advantages of ease ofapplication and low water vapor transmission rates demonstrated byhot-melt sealants as well as the strong chemical adhesion and structuralstrength exhibited by most room temperature vulcanizing sealants.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is an elevational view illustrating a sealed insulating glassunit of the present invention with portions broken away.

FIG. 2 is an enlarged sectional view along lines 2--2 of FIG. 1illustrating the disposition of the panes of glass and spacing memberand the channel about the periphery of the glass unit.

FIG. 3 is a similar view illustrating the application of a sealantcomposition into the channel about the periphery of the glass unit.

FIG. 4 is a view similar to FIG. 3 illustrating the application of heatto the sealant composition.

FIG. 5 is a greatly enlarged sectional view along lines 2--2 of FIG. 1illustrating the curing or crosslinking which occurs in the outerportion of the sealant composition on the application of heat.

FIG. 6 is a view similar to FIG. 3 illustrating a modified form ofspacing element which may be used in fabricating the insulating glassunit.

In accordance with the present invention there is provided a method offabricating an insulating glass unit which comprises disposing a spacingmember between panes of glass adjacent the edges thereof to hold saidpanes in a predetermined spaced relation, the spacing member and glasspanes cooperating to provide a channel about the assembly, applying apartially crosslinked hot-melt butyl rubber sealant composition intosaid channel, said sealant being in continuous contact with said glasspanes and spacing member and of a type such that substantially completecrosslinking will occur when the composition is heated to from about325° F. to about 425° F. and applying sufficient heat to the exteriorface of said sealant composition to raise the temperature of theoutermost portion of the sealant composition to from about 325° F. toabout 425° F. while the innermost portion of the sealant compositionremains at a temperature substantially below about 325° F. to about 425°F. forming a high-strength thermoset bond about the outer periphery ofthe channel while the innermost portion of the sealant compositionadjacent the spacing member remains partially crosslinked providing ahigh tack, adhesive bond about the inner periphery of the channel.

Considering the invention in greater detail in connection with theappended drawings, insulating glass units (the term glass unit in thespecification and claims refers to and includes insulating glasswindows, doors and other types of glazing units) are fabricated bydisposing sheets of glass 10 and 11 in predetermined spaced relation toone another by spacing member 12 so as to provide a dead air space 13between the sheets of glass.

The glass sheets 10 and 11 may be any conventional, commerciallyavailable glass cut to desired size. Spacing member 12 may be ofconventional type and cross-section, preferably hollow, and may containa desiccant material 17 such as silica gel and the like. The spacingmember may be formed of aluminum, galvanized steel or other metal andmay be fabricated by roll forming into a generally tubular configurationhaving a slightly open butt joint 14. The open butt joint 14communicates with dead air space 13 to enable desiccant material 17 todehydrate the air within the dead space thereby precluding condensationin the interior of the glass unit.

Spacing member 12 is located adjacent the edges of glass sheets 10 and11 about the periphery thereof positioned inward from the marginal edgesof the sheets defining in cooperation with sheets 10 and 11 an outwardlyfacing channel 15 extending about the entire periphery of the unit.Spacing member 12 may be of a generally rectangular configuration asshown in FIGS. 2-5. Spacing member 12 may also be of a configurationsuch as shown in FIG. 6, for example, wherein a somewhat larger surfacearea is presented for contact with bonding or sealant material and meansare provided to center spacing member 12 a between glass sheets 10 and11.

Bonding or sealant material 16 is supplied in channel 15 about theperiphery of the insulating glazing unit. Sealant material 16 is apartially crosslinked hot-melt butyl rubber composition which is appliedby means of any suitable hot-melt applicator capable of reducing thehot-melt sealant from a solid to a more or less viscous but non-saggingor thixotropic liquid state which will completely fill channel 15.Sufficient hot-melt sealant composition 16 is supplied to completelyfill channel 15 and overlap the edges of glass sheets 10 and 11 forminga complete seal about channel 15 as illustrated in FIG. 4. The hot-meltbutyl rubber sealant composition cools rapidly after application tochannel 15 and adheres physically by the tacky nature of theuncrosslinked sealant to panes of glass 10 and 11 and spacing member 12serving to hold the glass panes and spacing member in registry duringfurther assembly.

The hot-melt butyl rubber sealant is formulated so that substantiallycomplete crosslinking or curing will occur when the composition isheated to from about 325° F. to about 425° F., preferably about 400° F.After application of the hot-melt butyl rubber sealant, heat is appliedto the exterior face 16a of sealant material 16 as is shown in FIG. 4.Heat may be supplied by any conventional high heat flux source such asinfra red, super-heated air jets or open flame. The application of heatis carefully controlled to ensure that only the exterior portion ofhot-melt butyl rubber sealant 16, that is, that portion of the sealantcomposition which overlaps the ends of glass panes 10 and 11 and isadjacent to the outermost portions of glass panes 10 and 11, e.g. about30 to about 50% of the total sealant applied to the periphery of theinsulating glazing unit, will be heated to a temperature of from about325° F. to about 425° F. The interior portion of sealant 16, i.e., thatportion of sealant 16 which is adjacent to spacing member 12 and theinterior portion of glass panes 10 and 11 in channel 14, remains at atemperature below about 325° F. during the heating process.

Since the sealant 16 is formulated with agents effective to causecrosslinking of the hot-melt butyl rubber sealant when activated attemperatures of from about 325° F. to about 425° F., preferably about400° F., heating in the manner described causes sealant material 16 tocrosslink or cure in the area heated to temperatures of from about 325°F. to about 425° F. while the portion of sealant material 16 not heatedto about 325° F. to about 425° F. remains uncrosslinked. In this mannera dual sealant effect is obtained. The exterior and outer portion ofsealant 16 is completely thermoset as the result of crosslinking orcuring and exhibits excellent structural strength. It will not melt withsubsequent heating, and because of its strength, it is not necessary toprovide an outer web, band or other mechanical support about theperiphery of the insulating glass unit. At the same time, the interiorportion of sealant material 16 adjacent spacing member 12 remainsuncrosslinked in the form of a sticky mastic material which providesexcellent adhesion to glass panes 10 and 11 and spacing member 12, andprovides a barrier impervious to air, water vapor and the like.

The sealant material 16 forms a strong bond with glass panes 10 and 11,however, a coating of primer or a tie coat may be applied to the surfaceof the glass to be bonded prior to application of the sealant material.Also various silane compounds may be incorporated into the butyl rubbersealant to improve adhesion of the butyl polymer to glass and aluminum.The use of from about 2 to about 10 parts ofgamma-methacryl-oxypropyltrimethoxysilane per 100 parts of butyl rubber,for example, enhances the adhesion of the butyl polymer to glass andaluminum.

A variety of butyl polymers may be used in formulating the hot-meltsealant; for example, a blend of low molecular weight butyl polymerssuch as Exxon LM-430 butyl polymer and a partially crosslinked butylpolymer such as Cities Service Ex 245 in a ratio of about 2:1 willprovide a satisfactory sealant. The blend of butyl polymers is combinedwith a curing system for butyl rubber comprising an aromatic nitrogencontaining compound such as p-quinone dioxime, and an oxidizing agentsuch as red lead oxide. Butyl rubber curing systems comprising p-quinonedioxime and red lead oxide are well known in the art, and the mechanismthrough which curing of butyl rubber is accomplished is generallythought to involve oxidation of p-quinone dioxime by red lead oxide,forming in situ, the active crosslinking agent, p-dinitrosobenzene.

To form the desired sealant, a sufficient amount of each component ofthe curing system should be combined with the butyl polymer blend tocause complete crosslinking of that portion of the hot-melt sealantheated to a temperature from about 325° to about 425° F., preferablyabout 400° F. Thus, from about 2 to about 6, preferably about 3 parts ofp-quinone dioxime, and from about 4 to about 10, preferably about 8parts of red lead oxide, per 100 parts of butyl polymer blend arecombined to form the hot-melt sealant.

It has been found that the foregoing hot-melt sealant has propertieswhich make it particularly useful in the fabricating of insulating glassunits. For example, the hot-melt sealant softens to a viscous,thixotropic state when heated to temperatures of about 250° F. and has asufficient pot life when heated to this temperature to be easily appliedand completely fill channel 15. Also, it can be appreciated thatsignificant flexibility over the amount of sealant 16 which iscrosslinked can be achieved through control of the amount of heatapplied to sealant 16.

The following example is set forth for purposes of illustration of theinvention.

EXAMPLE 1

Glass panes 10 and 11 were assembled with spacing member 12, as shown inFIG. 1 forming a channel 15 about the peripheral edges of the panes. Asealant of the following formulation was applied to channel 15 by ahot-melt application to fill channel 15, overlapping the end of glasspanes 10 and 11.

    ______________________________________                                                               Weight                                                 ______________________________________                                        Butyl polymer                                                                 (Exxon LM-430)           1000                                                 Butyl polymer                                                                 (Cities Service EX 245)  500                                                  Chlorinated Paraffin                                                          (Pearsall Chemical FLX 0012)                                                                           160                                                  Neodecanoic acid         20                                                   Silane                                                                        (Union Carbide A-174)    60                                                   Rosin ester                                                                   (Arizona Chemical, Zonarex 55)                                                                         150                                                  Diamine antioxidant                                                           (Age Rite White)         30                                                   Benzothiazyl disulfide                                                        (Altax)                  40                                                   p-quinonedioxime         25                                                   Red Lead Oxide (Pb.sub.3 O.sub.4)                                                                      80                                                   Calcium carbonate        1200                                                 ______________________________________                                    

On cooling, a partially crosslinked butyl rubber polymer havingsufficient adhesion and strength to hold the assembly is formed. Heatwas applied to the exterior surface 16a of the butyl polymer causing thetemperature in the outer portion of the polymer to reach about 400° F.At this point, exterior portion 16a of the butyl sealant was completelycrosslinked providing structural strength and integrity to the glassunit, the inner portion of the butyl polymer remaining uncrosslinked andin a tacky form.

Having thus described the invention, what is claimed is:
 1. Aninsulating glass unit comprising glass panes held in a predeterminedspaced relation by a spacing member disposed between the panes of glassadjacent to the edges thereof and cooperating to provide a channel aboutthe periphery of the assembly and a partially crosslinked hot-melt butylrubber sealant composition in said channel in contact with said glasspanes and spacing member, sufficient heat having been applied to theexterior face of the sealant composition to raise the temperature of theoutermost portion of the sealant composition to above from about 325° F.to about 425° F. while the innermost portion of the sealant compositionremained at a temperature substantially below from about 325° F. toabout 425° F. to cause substantially complete crosslinking of thatportion of the sealant composition heated above from about 325° F. toabout 425° F. thereby forming a high-strength thermoset adhesive bondabout the outer periphery of the channel, while the innermost portion ofthe sealant composition adjacent the spacing member remaineduncrosslinked and provides a high tack, thermoplastic adhesive bondabout the inner periphery of the channel.
 2. The insulating glass unitof claim 1 wherein sufficient heat has been applied to the exterior faceof said sealant composition to raise the temperature of about 30 toabout 50% of the outermost portion of the sealant composition to fromabout 325° F. to about 425° F.